| UV irradiated gas sensors have recently attracted widespread interest,due to their simple structure,low cost,easy operation and room working temperature.However,the development of UV irradiated gas sensors with high performances,such as high sensitivity,fast response and recovery time,high stability and low detection limit,is still challenging.In this dissertation,on the basis of sensing materials and their structure adjustment,the effects of microstructure,morphology and irrelevant dimension on the gas sensing performances were investigated.We demonstrate a novel method of developing high performance under UV light irradiation,and their corresponding sensing perforamce studies.The main research results and novelties of the thesis are as follows.(1)Study of the effect microstructured parameters of mcrio/nanostructured ordered array thin films on gas sensing performaces.By changing the ordered array period,the relationship between the irrelevant size of ordered array and the gas sensing perfomace was explored.The optimal UV light power of the gas sensing performance was investigated,and the intrinsic mechanism of gas sensing enhancement characteristics of micro/nanostructured ordered array thin film is explained based on the correlation structure parameters of gas sensing performace.By changing the concentration of the precursor solution,two kinds of ordered porous array films with different structures were prepared,as follow:close-network and bowl-like micro/nanoporous arrays film.Compared with the bowl-like structure,the close-network has higher specific surface area and special ring structure,which can produce more photogenerated carriers and provide more active sites on the surface of the films under UV light irradiated.The results show that the close-network structure significantly enhanced NO2 gas sensing performance compared with the bowl-like structure.(2)Based on the phenomenological analyses of the porous thin films under light irradiation,we have established the analytical relationship between the response and the film's thickness for the irradiating-typed gas sensors.It was found that the responses of the semiconducting porous thin films to the test gases increase with the rising film-thickness and reach the maxima when the thicknesses are equal to the penetration depths of light in the films.Further increasing the thickness would lead to the insignificantly or a gradually decreasing responses,due to no further increasing photo-generated carriers.In order to validate the theoretical model,we investigated the effects of three different structures and thicknesses of different density films on the gas sensing properties of the oxidized gas.The analysis shows that the experimental results are in good agreement with the theoretical model.(3)We propose a facile and universal approach to fabricate substrate-independent hollow sphere arrays via template-assisted and hydrothermal,which realizes the control of metal oxide and organic semiconductor hollow sphere arrays deposited on any desired substrate.The mono/multilayer hollow sphere arrays with tunable shell thickness and sphere diameter have been successfully prepared,which will be of great significance in applications.By using this approach,we fabricated the iron oxide and Zinc Oxide hollow spheres arrays on flat electrode substrates and investigated their gas sensing properties.The results showed that iron oxide hollow sphere array film has good sensitivity and high selectivity to H2S at low temperature;ZnO porous hollow sphere array film has ultrafast response/recovery time and high sensitivity to NO2 under UV light irradiation.In this dissertation,the relationship between morphology parameters of micro/nanostructure and gas sensing performance under UV light irradiation,and the construction and optimization method of high performance gas sensor is developed.We have realized a high performance of gas sensor to hazardous gas,such as nitrogen dioxide,which has important application value. |
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